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  <title>ECMAScript 2015 Language Specification &ndash; ECMA-262 6th Edition</title>
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  <h1>Introduction</h1>

  <p>This Ecma Standard defines the ECMAScript 2015 Language. It is the sixth edition of the ECMAScript Language Specification.
  Since publication of the first edition in 1997, ECMAScript has grown to be one of the world&rsquo;s most widely used general
  purpose programming languages. It is best known as the language embedded in web browsers but has also been widely adopted for
  server and embedded applications. The sixth edition is the most extensive update to ECMAScript since the publication of the
  first edition in 1997.</p>

  <p>Goals for ECMAScript 2015 include providing better support for large applications, library creation, and for use of
  ECMAScript as a compilation target for other languages. Some of its major enhancements include modules, class declarations,
  lexical block scoping, iterators and generators, promises for asynchronous programming, destructuring patterns, and proper tail
  calls. The ECMAScript library of built-ins has been expanded to support additional data abstractions including maps, sets, and
  arrays of binary numeric values as well as additional support for Unicode supplemental characters in strings and regular
  expressions. The built-ins are now extensible via subclassing.</p>

  <p>ECMAScript is based on several originating technologies, the most well-known being JavaScript (Netscape) and JScript
  (Microsoft). The language was invented by Brendan Eich at Netscape and first appeared in that company&rsquo;s Navigator 2.0
  browser. It has appeared in all subsequent browsers from Netscape and in all browsers from Microsoft starting with Internet
  Explorer 3.0.</p>

  <p>The development of the ECMAScript Language Specification started in November 1996. The first edition of this Ecma Standard
  was adopted by the Ecma General Assembly of June 1997.</p>

  <p>That Ecma Standard was submitted to ISO/IEC JTC 1 for adoption under the fast-track procedure, and approved as international
  standard ISO/IEC 16262, in April 1998. The Ecma General Assembly of June 1998 approved the second edition of ECMA-262 to keep it
  fully aligned with ISO/IEC 16262. Changes between the first and the second edition are editorial in nature.</p>

  <p>The third edition of the Standard introduced powerful regular expressions, better string handling, new control statements,
  try/catch exception handling, tighter definition of errors, formatting for numeric output and minor changes in anticipation
  future language growth. The third edition of the ECMAScript standard was adopted by the Ecma General Assembly of December 1999
  and published as ISO/IEC 16262:2002 in June 2002.</p>

  <p>After publication of the third edition, ECMAScript achieved massive adoption in conjunction with the World Wide Web where it
  has become the programming language that is supported by essentially all web browsers. Significant work was done to develop a
  fourth edition of ECMAScript. However, that work was not completed and not published as the fourth edition of ECMAScript but
  some of it was incorporated into the development of the sixth edition.</p>

  <p>The fifth edition of ECMAScript (published as ECMA-262 5<sup>th</sup> edition) codified de facto interpretations of the
  language specification that have become common among browser implementations and added support for new features that had emerged
  since the publication of the third edition. Such features include accessor properties, reflective creation and inspection of
  objects, program control of property attributes, additional array manipulation functions, support for the JSON object encoding
  format, and a strict mode that provides enhanced error checking and program security. The Fifth Edition was adopted by the Ecma
  General Assembly of December 2009.</p>

  <p>The fifth Edition was submitted to ISO/IEC JTC 1 for adoption under the fast-track procedure, and approved as international
  standard ISO/IEC 16262:2011. Edition 5.1 of the ECMAScript Standard incorporated minor corrections and is the same text as
  ISO/IEC 16262:2011. The 5.1 Edition was adopted by the Ecma General Assembly of June 2011.</p>

  <p>Focused development of the sixth edition started in 2009, as the fifth edition was being prepared for publication. However,
  this was preceded by significant experimentation and language enhancement design efforts dating to the publication of the third
  edition in 1999. In a very real sense, the completion of the sixth edition is the culmination of a fifteen year effort.</p>

  <p>Dozens of individuals representing many organizations have made very significant contributions within Ecma TC39 to the
  development of this edition and to the prior editions. In addition, a vibrant informal community has emerged supporting
  TC39&rsquo;s ECMAScript efforts. This community has reviewed numerous drafts, filed thousands of bug reports, performed
  implementation experiments, contributed test suites, and educated the world-wide developer community about ECMAScript.
  Unfortunately, it is impossible to identify and acknowledge every person and organization who has contributed to this
  effort.</p>

  <p>New uses and requirements for ECMAScript continue to emerge. The sixth edition provides the foundation for regular,
  incremental language and library enhancements.</p>

  <p>Allen Wirfs-Brock<br>ECMA-262, 6<sup>th</sup> Edition Project Editor</p>

  <p>This Ecma Standard has been adopted by the General Assembly of June 2015.</p>
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